The present invention is directed to phase change ink compositions. More specifically, the present invention is directed to phase change ink compositions particularly suitable for use in hot melt acoustic ink jet printing processes. One embodiment of the present invention is directed to a phase change ink comprising (a) a carbamate or thiourea, said carbamate or thiourea having a melting point of no higher than about 120.degree. C. and an acoustic loss value of no more than about 100 decibels per millimeter, (b) a colorant, (c) a branched hydrocarbon with a number average molecular weight of no more than about 10,000 and a melting point or softening point of no more than about 120.degree. C., (d) an optional plasticizer, (e) an optional alcohol having a melting point of less than about 90.degree. C. and an acoustic loss value of no more than about 100 decibels per millimeter, (f) an optional lightfastness-imparting agent, and (g) an optional antioxidant,
Acoustic ink jet printing processes are known. In acoustic ink jet printing processes, an acoustic beam exerts a radiation pressure against objects upon which it impinges. Thus, when an acoustic beam impinges on a free surface (i.e., liquid/air interface) of a pool of liquid from beneath, the radiation pressure which it exerts against the surface of the pool may reach a sufficiently high level to release individual droplets of liquid from the pool, despite the restraining force of surface tension. Focusing the beam on or near the surface of the pool intensifies the radiation pressure it exerts for a given amount of input power. These principles have been applied to prior ink jet and acoustic printing proposals. For example, K. A. Krause, "Focusing Ink Jet Head,"IBM Technical Disclosure Bulletin, Vol. 16, No. 4, September 1973, pp. 1168-1170, the disclosure of which is totally incorporated herein by reference, describes an ink jet in which an acoustic beam emanating from a concave surface and confined by a conical aperture was used to propel ink droplets out through a small ejection orifice. Acoustic ink printers typically comprise one or more acoustic radiators for illuminating the free surface of a pool of liquid ink with respective acoustic beams. Each of these beams usually is brought to focus at or near the surface of the reservoir (i.e., the liquid/air interface). Furthermore, printing conventionally is performed by independently modulating the excitation of the acoustic radiators in accordance with the input data samples for the image that is to be printed, This modulation enables the radiation pressure which each of the beams exerts against the free ink surface to make brief, controlled excursions to a sufficiently high pressure level for overcoming the restraining force of surface tension. That, in turn, causes individual droplets of ink to be ejected from the free ink surface on demand at an adequate velocity to cause them to deposit in an image configuration on a nearby recording medium. The acoustic beam may be intensity modulated or focused/defocused to control the ejection timing, or an external source may be used to extract droplets from the acoustically excited liquid on the surface of the pool on demand. Regardless of the timing mechanism employed, the size of the ejected droplets is determined by the waist diameter of the focused acoustic beam. Acoustic ink printing is attractive because it does not require the nozzles or the small ejection orifices which have caused many of the reliability and pixel placement accuracy problems that conventional drop on demand and continuous stream ink jet printers have suffered. The size of the ejection orifice is a critical design parameter of an ink jet because it determines the size of the droplets of ink that the jet ejects. As a result, the size of the ejection orifice cannot be increased, without sacrificing resolution. Acoustic printing has increased intrinsic reliability because there are no nozzles to clog. As will be appreciated, the elimination of the clogged nozzle failure mode is especially relevant to the reliability of large arrays of ink ejectors, such as page width arrays comprising several thousand separate ejectors. Furthermore, small ejection orifices are avoided, so acoustic printing can be performed with a greater variety of inks than conventional ink jet printing, including inks having higher viscosities and inks containing pigments and other particulate components. It has been found that acoustic ink printers embodying printheads comprising acoustically illuminated spherical focusing lenses can print precisely positioned pixels (i.e., picture elements) at resolutions which are sufficient for high quality printing of relatively complex images. It has also been discovered that the size of the individual pixels printed by such a printer can be varied over a significant range during operation, thereby accommodating, for example, the printing of variably shaded images Furthermore, the known droplet ejector technology can be adapted to a variety of printhead configurations, including (1) single ejector embodiments for raster scan printing, (2) matrix configured ejector arrays for matrix printing, and (3) several different types of pagewidth ejector arrays, ranging from single row, sparse arrays for hybrid forms of parallel/serial printing to multiple row staggered arrays with individual ejectors for each of the pixel positions or addresses within a pagewidth image field (i.e., single ejector/pixel/line) for ordinary line printing. Inks suitable for acoustic ink jet printing typically are liquid at ambient temperatures (i.e., about 25.degree. C.), but in other embodiments the ink is in a solid state at ambient temperatures and provision is made for liquefying the ink by heating or any other suitable method prior to introduction of the ink into the printhead. Images of two or more colors can be generated by several methods, including by processes wherein a single printhead launches acoustic waves into pools of different colored inks. Further information regarding acoustic ink jet printing apparatus and processes is disclosed in, for example, U.S. Pat. No. 4,308,547, U.S. Pat. No. 4,697,195, U.S. Pat. No. 5,028,937, U.S. Pat. No. 5,041,849, U.S. Pat. No. 4,751,529, U.S. Pat. No. 4,751,530, U.S. Pat. No. 4,751,534, U.S. Pat. No. 4,801,953, U.S. Pat. No. 4,797,693, U.S. Pat. No. 5,121,141, U.S. Pat. No. 5,111,220, U.S. Pat. No. 5,128,726, and U.S. Pat. No. 5,371,531, the disclosures of each of which are totally incorporated herein by reference. The use of focused acoustic beams to eject droplets of controlled diameter and velocity from a free-liquid surface is also described in J. Appl. Phys., vol. 65, no. 9 (May 1, 1989) and references therein, the disclosure of which is totally incorporated herein by reference.
In acoustic ink printing processes, the printhead produces approximately 2.2 picoliter droplets by an acoustic energy process. The ink under these conditions preferably displays a melt viscosity of from about 1 to about 25 centipoise at the jetting temperature. In addition, once the ink has been jetted onto the printing substrate, the image thus generated preferably exhibits excellent crease properties, and is nonsmearing, waterfast, of excellent transparency, and of excellent fix. The vehicle preferably displays a low melt viscosity in the acoustic head while also displaying solid like properties after being jetted onto the substrate. Since the acoustic head can tolerate temperatures typically up to about 180.degree. C., the vehicle for the ink preferably displays liquid-like properties (such as a viscosity of from about 1 to about 25 centipoise) at a temperature of from about 75 to about 180.degree. C., and solidifies or hardens after being jetted onto the substrate such that the resulting image exhibits a hardness value of from about 0.1 to about 0.5 millimeter (measured with a penetrometer according to the ASTM penetration method D1321).
Ink jet printing processes that employ inks that are solid at room temperature and liquid at elevated temperatures are known. For example, U.S. Pat. No. 4,490,731 (Vaught), the disclosure of which is totally incorporated herein by reference, discloses an apparatus for dispensing solid inks for printing on a substrate such as paper. The ink vehicle is chosen to have a melting point above room temperature so that the ink, which is melted in the apparatus, will not be subject to evaporation or spillage during periods of nonprinting. The vehicle selected possesses a low critical temperature to permit the use of the solid ink in a thermal ink jet printer. In thermal ink jet printing processes employing these phase change inks, the solid ink is melted by a heater in the printing apparatus and used as a liquid in a manner similar to that of conventional piezoelectric or thermal ink jet printing. Upon contact with the printing substrate, the molten ink solidifies rapidly, enabling the dye to remain on the surface instead of being carried into the paper by capillary action, thereby enabling higher print density than is generally obtained with liquid inks. After the phase change ink is applied to the substrate, freezing on the substrate resolidifies the ink.
U.S. Pat. No. 4,751,528 (Spehrley, Jr. et al.), the disclosure of which is totally incorporated herein by reference, discloses a hot melt ink jet system which includes a temperature-controlled platen provided with a heater and a thermoelectric cooler electrically connected to a heat pump and a temperature control unit for controlling the operation of the heater and the heat pump to maintain the platen temperature at a desired level. The apparatus also includes a second thermoelectric cooler to solidify hot melt ink in a selected zone more rapidly to avoid offset by a pinch roll coming in contact with the surface of the substrate to which hot melt ink has been applied. An airtight enclosure surrounding the platen is connected to a vacuum pump and has slits adjacent to the platen to hold the substrate in thermal contact with the platen.
U.S. Pat. No. 4,791,439 (Guiles), the disclosure of which is totally incorporated herein by reference, discloses an ink jet apparatus for use with hot melt ink having an integrally connected ink jet head and reservoir system, the reservoir system including a highly efficient heat conducting plate, such as aluminum, inserted within an essentially non-heat conducting reservoir housing. The reservoir system has a sloping flow path between an inlet position and a sump from which ink is drawn to the head, and includes a plurality of vanes situated upon the plate for rapid heat transfer.
U.S. Pat. No. 5,006,170 (Schwarz et al.) and U.S. Pat. No. 5,122,187 (Schwarz et al.), the disclosures of each of which are totally incorporated herein by reference, disclose hot melt ink compositions suitable for ink jet printing which comprise a colorant, a binder, and a propellant selected from the group consisting of hydrazine; cyclic amines; ureas; carboxylic acids; sulfonic acids; aldehydes; ketones; hydrocarbons; esters; phenols; amides; imides; halocarbons; urethanes; ethers; sulfones; sulfamides; sulfonamindes; phosphites; phosphonates; phosphates; alkyl sulfines; alkyl acetates; and sulfur dioxide. Also disclosed are hot melt ink compositions suitable for ink jet printing which comprise a colorant a propellant, and a binder selected from the group consisting of rosin esters; polyamides; dimer acid amides; fatty acid amides; epoxy resins; fluid paraffin waxes; fluid microcrystalline waxes; Fischer-Tropsch waxes; polyvinyl alcohol resins; polyols; cellulose esters; cellulose ethers; polyvinyl pyridine resins; fatty acids; fatty acid esters; poly sulfonamides; benzoate esters; long chain alcohols; phthalate plasticizers; citrate plasticizers; maleate plasticizers; sulfones; polyvinyl pyrrolidinone copolymers; polyvinyl pyrrolidone/polyvinyl acetate copolymers; novalac resins; natural product waxes; mixtures of linear primary alcohols and linear long chain amides; and mixtures of linear primary alcohols and fatty acid amides. In one embodiment the binder comprises a liquid crystalline material,
U.S. Pat. No. 5,041,161 (Cooke et al,), the disclosure of which is totally incorporated herein by reference, discloses an ink jet ink which is semi-solid at room temperature. The subject ink combines the advantageous properties of thermal phase change inks and liquid inks. More particularly, the inks comprise vehicles, such as glyceryl esters, polyoxyethylene esters, waxes, fatty acids, and mixtures thereof, which are semi-solid at temperatures between 20.degree. and 45.degree. C. The ink is impulse jetted at an elevated temperature in the range of above 45.degree. C. to about 110.degree. C., at which temperature the ink has a viscosity of about 10 to 15 centipoise. The subject inks exhibit controlled penetration and spreading, but do not remain on the surface of most substrates where they would be prone to burnishing, cracking or flaking. These inks further comprise 0.1 to 30 weight percent of a colorant system.
U.S. Pat. No. 4,853,036 (Koike et al.) and U.S. Pat. No. 5,124,718, the disclosures of each of which are totally incorporated herein by reference, disclose an ink for ink jet recording which comprises a liquid composition essentially comprising a coloring matter, a volatile solvent having a vapor pressure of 1 mm Hg or more at 25.degree. C., and a material being solid at room temperature and having a molecular weight of 300 or more; and prepared so as to satisfy formula B.sub.1 /A.sub.1.gtoreq.3, assuming viscosity as A.sub.1 cP at 25.degree. C. measured when the content of the solid material in said composition is 10 percent by weight, and assuming viscosity as B.sub.1 cP at 25.degree. C. measured when the content of the solid material in said composition is 30 percent by weight. An ink jet recording process employing the ink is also provided.
In phase change printing processes, the ink preferably undergoes a change with temperature from a solid state to a liquid state in a desirably short period of time, typically in less than about 100 milliseconds. One advantage of phase change inks is their ability to print superior images on plain paper, since the phase change ink quickly solidifies as it cools, and, since it is primarily waxy in nature, it does not normally soak into a paper medium.
Phase change inks also preferably exhibit a high degree of transparency, generally measured in terms of haze value of the ink. Transparent, low haze inks exhibit high gloss and high optical density compared to opaque inks, although both may appear to be evenly colored.
The use of phase change inks in acoustic ink printing processes is also known. U.S. Pat. No. 4,745,419 (Quate et al.), the disclosure of which is totally incorporated herein by reference, discloses acoustic ink printers of the type having a printhead including one or more acoustic droplet ejectors for supplying focused acoustic beams. The printer comprises a carrier for transporting a generally uniformly thick film of hot melt ink across its printhead, together with a heating means for liquefying the ink as it nears the printhead. The droplet ejector or ejectors are acoustically coupled to the ink via the carrier, and their output focal plane is essentially coplanar with the free surface of the liquefied ink, thereby enabling them to eject individual droplets of ink therefrom on command. The ink, on the other hand, is moved across the printhead at a sufficiently high rate to maintain the free surface which it presents to the printhead at a substantially constant level. A variety of carriers may be employed, including thin plastic and metallic belts and webs, and the free surface of the ink may be completely exposed or it may be partially covered by a mesh or perforated layer. A separate heating element may be provided for liquefying the ink, or the lower surface of the carrier may be coated with a thin layer of electrically resistive material for liquefying the ink by localized resistive heating.
U.S. Pat. No. 5,541,627 (Quate), the disclosure of which is totally incorporated herein by reference, discloses a method and apparatus for ejecting droplets from the crests of capillary waves riding on the free surface of a liquid by parametrically pumping the capillary waves with electric fields from probes located near the crests. Crest stabilizers are beneficially used to fix the spatial locations of the capillary wave crests near the probes. The probes are beneficially switchably connected to an AC voltage supply having an output that is synchronized with the crest motion. When the AC voltage is applied to the probes, the resulting electric field adds sufficient energy to the system so that the surface tension of the liquid is overcome and a droplet is ejected. The AC voltage is synchronized such that the droplet is ejected about when the electric field is near is minimum value. A plurality of droplet ejectors are arranged and the AC voltage is switchably applied so that ejected droplets form a predetermined image on a recording surface. The capillary waves can be generated on the free surface of the liquid by using acoustical energy at a level approaching the onset of droplet ejection. The liquid used with the invention must also be attracted by an electric field.
Phase change inks used in acoustic ink printing processes also preferably exhibit a low acoustic loss value, typically below about 100 decibels per millimeter. In addition, the ink vehicle preferably can fill the pores of a porous substrate, such as paper, and preferably has a melting point of from about 80 to about 120.degree. C.; this melting point, along with low acoustic loss, enables a minimization of energy consumption, When the phase change inks are used in an electric field assisted acoustic ink printing process, the inks also are sufficiently conductive to permit the transmission of electrical signals generated by the electric field assisted acoustic ink jet printer; the inks preferably exhibit a conductivity of from about 2 to about 9 log(picomho/cm) (measured under melt conditions at about 150.degree. C. by placing an aluminum electrode in the molten ink and reading the resistivity output on a GenRad 1689 precision RLC Digibridge at a frequency of 1 kiloHertz). In general, the conductivity of a material can be measured in terms of the reciprocal of resistivity, which is the capacity for electrical resistance. Further information regarding electric field assisted acoustic ink printing processes is disclosed in, for example, Copending Application U.S. Ser. No. 09/280,717, filed Mar. 30, 1999, entitled "Method and Apparatus for Moving Ink Drops using an Electric Field and Transfuse Printing System Using the Same," with the named inventors John S. Berkes, Vittorio R. Castelli, Scott A. Elrod, Gregory J. Kovacs, Meng H. Lean, Donald L. Smith, Richard G. Stearns, and Joy Roy, the disclosure of which is totally incorporated herein by reference, which discloses a method of forming and moving ink drops across a gap between a printhead and a print medium or intermediate print medium in a marking device. The method includes generating an electric field, forming the ink drops adjacent to the printhead, and controlling the electric field. The electric field is generated to extend across the gap. The ink drops are formed in an area adjacent to the printhead. The electric field is controlled such that an electrical attraction force exerted on the formed ink drops by the electric field is the greatest force acting on the ink drops. The marking device can be incorporated into a transfuse printing system having an intermediate print medium made of one or more materials that allow for lateral dissipation of electrical charge from the incident ink drops.
U.S. Pat. No. 6,045,607 (Breton et al.), the disclosure of which is totally incorporated herein by reference, discloses an ink composition containing (1) a first solid carbamate, (2) a second carbamate with a dissimilar melting point than the first solid carbamate (1), (3) a lightfastness component, (4) a lightfastness antioxidant, and (5) a colorant.
U.S. Pat. No. 5,932,630 (Kovacs et al.), the disclosure of which is totally incorporated herein by reference, discloses a hot melt ink composition comprising a triblock copolymer vehicle, and a dye or pigment.
U.S. Pat. No. 5,931,995 (Malhotra et al.), the disclosure of which is totally incorporated herein by reference, discloses an ink comprising (1) a liquid aldehyde, a liquid acid, or mixtures thereof, (2) a solid additive aldehyde compound, a solid additive acid compound, or mixtures thereof, (3) a lightfastness UV absorber, (4) a lightfastness antioxidant, and (5) a colorant.
U.S. Pat. No. 5,902,390 (Malhotra et al.), the disclosure of which is totally incorporated herein by reference, discloses an ink comprising (1) a liquid ketone, (2) a solid ketone, (3) a lightfastness UV absorber, (4) a lightfastness antioxidant, and (5) a colorant.
U.S. Pat. No. 5,876,492 (Malhotra et al.), the disclosure of which is totally incorporated herein by reference, discloses an ink comprising (1) a liquid ester vehicle, (2) a solid ester compound, (3) a liquid crystalline ester compound, (4) a UV absorber, (5) an antioxidant, and (6) a colorant.
U.S. Pat. No. 5,922,117 (Malhotra et al.), the disclosure of which is totally incorporated herein by reference, discloses an ink composition comprising (1) a liquid alcohol vehicle, (2) a solid alcohol compound, (3) a quaternary compound, (4) a lightfastness UV absorber, (5) a lightfastness antioxidant, and (6) a colorant.
U.S. Pat. No. 5,958,119 (Malhotra et al.), the disclosure of which is totally incorporated herein by reference, discloses an ink composition comprising (1) a liquid cyclic vehicle (2) a cyclic compound, (3) a liquid crystalline nitrile compound, (4) a lightfastness UV absorber, (5) a lightfastness antioxidant, and (6) a colorant.
U.S. Pat. No. 5,667,568 (Sacripante et al.), the disclosure of which is totally incorporated herein by reference, discloses an ink composition comprising a colorant and a bisamide with a viscosity of from about 1 centipoise to about 20 centipoise at a temperature of from about 125.degree. to about 185.degree. C., and which bisamide is of the formula ##STR2##
wherein R is an alkyl of from about 2 to about 30 carbon atoms or aryl, R' is an alkylene with from about 2 to about 30 carbon atoms, or R' is a polyalkyleneoxide with from about 2 to about 30 carbon atoms.
U.S. Pat. No. 5,698,017 (Sacripante et al.), the disclosure of which is totally incorporated herein by reference, discloses an ink composition comprising a colorant and a vehicle component, and which vehicle component comprises the condensation product of an organic acid and an amino alcohol.
U.S. Pat. No. 5,693,128 (Sacripante et al.), the disclosure of which is totally incorporated herein by reference, discloses an ink composition comprising a colorant and a reversible crosslinked component vehicle obtained from the reaction product of an anhydride and an organoamine, and which ink possesses a viscosity of from about 1 centipoise to about 25 centipoise at a temperature of from about 125.degree. C. to about 185.degree. C.
U.S. Pat. No. 5,700,316 (Pontes et al.), the disclosure of which is totally incorporated herein by reference, discloses an ink composition comprising a colorant and a vehicle of a poly(alkylene oxide)-alkylate (1), a poly(alkylene oxide)-dialkylate (II), a polyoxa-alkanoate ester (III), or a polyoxa-alkanedioate diester (IV), and which ink possesses a viscosity of from about 1 centipoise to about 15 centipoise at a temperature of from about 125.degree. C. to about 165.degree. C., and which vehicle is of the formulas ##STR3##
wherein R is alkyl, R' is an alkylene, or arylene, and n is an integer of from about 2 to about 20.
U.S. Pat. No. 5,989,325 (Sacripante et al.), the disclosure of which is totally incorporated herein by reference, discloses nonaqueous ink composition comprising a vehicle, colorant, and a hydrophobic gelling component.
U.S. Pat. No. 5,954,866 (Ohta et al.), the disclosure of which is totally incorporated herein by reference, discloses an ink composition for ink jet recording which can meet many property requirements for an ink composition used in ink jet recording and, in addition, can yield a good image on a recording medium having a layer comprising a water-soluble resin. An ink jet recording method using the same is also provided. An ink composition comprising a pigment as a colorant, an anionic surfactant having a polyoxyethylene group, a dispersant, and water is used to record an image on a recording medium having a layer comprising a water-soluble resin by ink jet recording.
U.S. Pat. No. 5,098,477 (Vieira et al.), the disclosure of which is totally incorporated herein by reference, discloses inks, particularly inks for ink jet printing, contain at least one compound of the formula ##STR4##
as a stabilizer. The compounds are in part novel and are suitable for use as light stabilizers for organic materials.
U.S. Pat. No. 5,693,126 (Vieira et al.), the disclosure of which is totally incorporated herein by reference, discloses a water-based ink composition which can provide a print having better water resistance, stably contains a colorant virtually insoluble or sparingly soluble in water, is less likely to cause clogging of a recording head, and can be advantageously used for ink jet recording. The water-based ink composition comprises a colorant which is either sparingly soluble or insoluble in water; a solid solvent which is solid at room temperature and soluble in water and can dissolve, in the form of a hot melt or aqueous solution thereof, the colorant and, can form a solid solution together with the colorant; and water.
U.S. Pat. No. 5,948,155 (Yui et al.), the disclosure of which is totally incorporated herein by reference, discloses an ink jet recording ink and an ink jet recording method, said ink jet recording ink comprising a water-insoluble coloring material, water, and at least one compound selected from the group consisting of a compound represented by formula (I) and polyglycerin: ##STR5##
wherein R represents H or an alkyl group having 1 to 5 carbon atoms; m, n, o and p are all integers; and m+n+o+p is 0 to 200.
U.S. Pat. No. 5,897,940 (Malhotra), the disclosure of which is totally incorporated herein by reference, discloses a transparency comprising a supporting substrate, and thereover and thereunder two coatings, a first heat dissipating and fire resistant coating layer in contact with the substrate, and wherein said first coating comprises a binder with a melting point in the range of from about 100.degree. C. to about 275.degree. C. and a heat dissipating fire retardant component; and in contact with each of said first layers a second ink receiving coating layer thereover comprising a blend of a binder polymer, a cationic component capable of complexing with ink composition dyes, a lightfastness inducing agent, a filler, a biocide, and an ink spreading fluoro compound containing from 1 to about 25 fluorines and wherein said fluoro compound possesses a melting point of between about 50.degree. C. and about 100.degree. C.,
U.S. Pat. No. 5,538,550 (Yaegashi et al.), the disclosure of which is totally incorporated herein by reference, discloses a normally solid recording material that is heat-melted in a path defined by a nozzle leading to an ejection outlet and is imparted with a thermal energy from a heater corresponding to a recording signal to generate a bubble. As a result, a droplet of the recording material is ejected out of the ejection outlet under the action of the bubble while the bubble is caused to communicated with ambience The normally solid recording material preferably contains a colorant, a first heat-fusible solid substance having a melting point Tm of 36.degree. to 150.degree. C. and a boiling point Tb of 150.degree. to 370.degree. C., and a second heat-fusible solid substance having a melting point Tm and a solidifying point Tf satisfying a relationship of Tm-Tf.ltoreq.30.degree. C. The distance between the heater and the ejection outlet, the sectional size of the nozzle, and the thermal energy imparted by the heater are controlled to cause the bubble to communicate with ambience.
U.S. Pat. No. 3,953,218 (Pollard), the disclosure of which is totally incorporated herein by reference, discloses fatty acid amide coated pigments that are obtained and used to formulate with thermoplastic or thermoset materials. The colors of the pigments are fully developed and extremely high pigment loadings are obtained. The coated pigments are formed by admixing the pigment with melted fatty acid amide; solidifying the material by cooling it; grinding the material; and separating out the fines. The coated pigment particles are compounded with thermoplastic or thermoset materials by low shear means, such as, injection molding. An improved form of the coated pigments can be obtained by admixing the melted fatty acid amide and the pigment, extruding the admixture to form a creamy mass; solidifying and forming the creamy mass by passing it through cold and forming rollers, grinding the resultant wafer-like material; and separating out the fines. Liquid compositions of fatty acid amide coated pigments can be obtained by admixing pigment particles and a fatty acid amide which is liquid at room temperature or by admixing a fatty acid amide, pigment particles and a non-solvent diluent which is liquid at room temperature.
While known compositions and processes are suitable for their intended purposes, a need remains for acoustic phase change ink compositions suitable for ink jet printing. In addition, a need remains for phase change ink compositions that are compatible with a wide variety of plain papers and can generate photographic quality images on plain and coated papers. Further, a need remains for phase change ink compositions that generate high quality, lighffast, and waterfast images on plain papers. Additionally, a need remains for phase change ink jet inks that generate high quality, fast-drying images on a wide variety of plain papers at low cost with high quality text and high quality graphics, and wherein the dye may be retained on the paper surface while the ink vehicle can continue to spread within the paper structure. There is also a need for phase change ink jet inks that exhibit minimal feathering. In addition, there is a need for phase change ink jet inks that exhibit minimal intercolor bleed. Further, there is a need for phase change ink jet inks that exhibit excellent image permanence. Additionally, there is a need for phase change ink jet inks that are suitable for use in acoustic ink jet printing processes. A need also remains for phase change hot melt ink compositions suitable for ink jet printing processes wherein the substrate is heated prior to printing and is cooled to ambient temperature subsequent to printing (also known as heat and delay printing processes). In addition, a need remains for ink compositions suitable for ink jet printing wherein high optical densities can be achieved with relatively low dye concentrations. Further, a need remains for ink compositions suitable for ink jet printing wherein curling of the substrate subsequent to printing is minimized or avoided. Additionally, a need remains for phase change ink compositions that generate images with reduced susceptibility to creasing. There is also a need for phase change ink compositions that generate images of high transparency and light transmission. In addition, there is a need for phase change ink compositions that generate images with improved projection efficiency. Further, there is a need for phase change ink compositions with desirably low viscosities at the temperatures at which a hot melt ink jet printer is operated. Additionally, there is a need for phase change inks with desirably low acoustic loss values. A need also remains for phase change inks that can enable production of high quality images in a hot melt acoustic ink jet printer at temperatures of 100OC or less. In addition, a need remains for phase change inks that can generate images with high projection efficiency without the need for a fusing step subsequent to jetting. Further, a need remains for phase change inks for which the spherulite (spherical ink crystals) size is reduced. Additionally, a need remains for phase change inks that can generate images easily copied in a conventional photocopier because of a desirably low coefficient of friction of the images.